Field of the Invention
The invention relates to a luminaire having a curved reflector and a light permeable diffuser arranged neighboring a lamp and spaced apart in a manner to define a light chamber having a light entry surface which defines a height near the lamp, and running together at their ends away from the lamp to define a width extending from the light entry surface.
A luminaire of this kind, as is described for example in DE 44 43 916 A1, is illustrated in FIG. 14. There, arranged below an elongate gas discharge lamp 21, there is a raster reflector 26 consisting of side reflectors and transverse lamellae, with the aid of which raster reflector the greater part of the light emitted by the lamp 21 is directed and emitted downwardly without a dazzling effect. The employment of such a raster reflector 26 is of advantage for example in the case of luminaires in offices with many computer-screen work stations, since the light emitted downwardly is to a certain degree made transversely non-dazzling and thus can cause no reflections on the screens.
The luminaire illustrated in FIG. 14 of DE 44 43 916 A1 has further a concavely curved outer reflector 22 onto which there falls light emitted by the lamp 21 to the sides or upwardly. In this manner, the region surrounding the lamp 21 and the raster reflector 26 is additionally brightened, which on the one hand makes it possible to recognize in a simple manner whether the luminaire is in fact switched on or off, but on the other hand is also perceived by an observer as significantly more pleasant than the light of a pure raster luminaire, with which the entire light is emitted solely downwardly, so that the ceiling region itself appears dark.
With such lamps it is as a rule desired that the region surrounding the lamp appears with a uniformity of brightness. This problem is addressed for example also in DE 43 36 923 A1. Thus, as a rule, the outer reflector of such a luminaire has a particular curvature, exactly calculated in advance, which reflects the light emitted to the sides from the lamp in such a manner that the outer reflector appears uniformly bright. However, this mostly has the consequence that the outer reflector, due to this predetermined curvature, has a relatively great height and slight width, so that overall the luminaire is very high. If, on the contrary, the outer reflector 22 were configured to be flatter, this would have the consequence that the light density in the regions of the outer reflector 22 neighboring the lamp 22 is higher than at the edge of the reflector. With the luminaire illustrated in FIG. 14 a uniform distribution of brightness is additionally supported in that below the outer reflector 22 there is arranged a translucent (opalescent) plate 23. Overall, however, this luminaire also has a relatively great height.
It is the object of the present invention to provide a luminaire which has a significantly less height than the known luminaires and with regard to its form offers more possibilities for design variations.
The luminaire in accordance with the invention has a tube-shaped gas discharge lamp, at least one concavely curved reflector arranged, seen from the region to be illuminated, neighboring the lamp and at least one at least partially light permeable diffusor arranged, likewise seen from the region to be illuminated, +neighboring the lamp but before the reflector. The diffusor and the reflector bound next to the lamp at least one light entry surface and so run together at their ends away from the lamp that they enclose at least one light chamber. In accordance with the invention the ratio between the width of a light chamber and the height of a light entry surface is at least 4:1, whereby by the height of the light entry surface there is to be understood the spacing between the reflector and the diffusor present in this region. This measure has the consequence that the luminaire can be configured overall significantly flatter, and further the possibility arises of giving the luminaire a completely new appearance.
For the case that the greatest spacing between the reflector and diffusor is greater than the height of the light entry surface, the ratio of the width of a light chamber to the greatest spacing is preferably at least 4:1. Particularly preferably the ratio of the width of a light chamber to the height of the light entry surface, or to the greatest spacing between the reflector and the diffusor, lies between 4:1 and 5:1.
For attaining a uniform light density over the reflector cross-section there may be provided a plurality of additional means on the luminaire. Preferably for example the light entry surfaces for the light chamber or light chambers are likewise formed by means of diffusors. A further possibility consists in that the light entry surfaces are so formed that a high proportion of the light emitted from the lamp into a light chamber is deflected onto more distant regions of the reflector. For this purpose the above-mentioned diffusers, forming the light entry surfaces, may for example have different light permeabilities, or there exists the possibility to arrange optical elementsxe2x80x94for example prism structures or the likexe2x80x94in the light entry surface, which deflect the light in the desired manner onto the reflector. Preferably, the surface of the deflector is likewise diffusely reflective, but it can also be so configured that the regions lying more distant from the lamp have a higher degree of reflection than the regions near to the lamp, which likewise encourages uniformity of the light density. A further measure can consist in that the diffusor arranged before the reflector also has a light permeability dependent upon the distance to the lamp.
In order to be able to employ the light emitted from the lamp downwardly for effective illumination there may be arranged below the lamp a light distributor element, for example a raster consisting of side reflectors and transverse lamellae. Other optical elements would also be conceivable, which bring about an interesting appearance of the overall luminaire, for example a partially light permeable perforated sheet or the like.
Further developments of the luminaire can consist in that the reflector arranged to the sides of the lamp is itself partially permeable. There then exist the possibility of arranging behind this partially light permeable reflector further light sources, which can be employed for the attainment of particular lighting effects. On the other hand, in this case a ceiling region lying above the luminaire can also be brightened.
If the reflector is partially light permeable, a further development can thus also consist in arranging behind the reflector a further reflector so that behind the light chambers in each case a further light chamber is formed. There then exists the possibility of providing additional light sources within these further light chambers, which for example may be controllable in their color and brightness. Here, for example, controllable light emitting diodes (LED""S) may be involved. Thereby, again, a multiplicity of different lighting effects can be attained. The formation of this additional light chamber or light chambers may be effected, however, also independently of the above-indicated size ratio for a light chamber.
Finally, for attaining a further new lighting effect it may also be provided that within the light entry surface there are arranged optical elements which bring about a color change of the light on the reflector, so that the region surrounding the lamp appears in a somewhat different color.
The luminaire in accordance with the invention can find employment in a plurality of different types of luminaire.